In a large mixing bowl, combine the ground beef, bread crumbs, milk, egg, finely chopped onion, minced garlic, salt, and black pepper.

Transfer the meat mixture onto a baking sheet lined with parchment paper or into a greased loaf pan and shape into a log.

In a separate bowl, mix together the ketchup, brown sugar, and mustard until well combined. Spread half of the glaze over the meatloaf.

Preheat your oven to 350°F (175°C) and bake the meatloaf for about 1 hour, brushing remaining glaze during the last 10 minutes.

Remove the meatloaf from the oven and let it rest for 10-15 minutes before slicing to allow the juices to redistribute.